Typewriter key locking attachment



Feb. 27, 1940. M, F, CQQKE 2,191,706

TYPEWRIT ER KEY LOCKING ATTACHMENT Filed Aug. 14, 1939 Patented Feb. 27, 1940 UNITED STATES PATENT OFFICE The invention relates to improvements in typewriter key locking attachments and more particularly to a novel attachment of this type especially suited for use on a power actuated typewriter.

One main object of the invention is to provide a novel typewriter attachment for automatically locking the key-levers against movement when the carriage reaches a selected limit position,

and which is of such character as to insure effectual and accurate operation without danger of inadvertent locking when the carriage is short of its limit position, despite vibration incident to the operation of a heavy power driven type- 1 writer.

A more specific object is to provide an attachment of the character indicated embodying a normally engaged key-lever lock having an electromagnetic lock-releasing mechanism together 2 with a novel switch arrangement adapted to deenergize the lock-releasing mechanism, when the carriage reaches its limit position, so as to per mit the lock to lock the key-levers, and also adapted to reenergize the lock-releasing mechanism in response to the release of a mechanical stop mechanism which normally serves to stop the carriage in its limit position.

Another object is to provide an attachment of the character indicated which may be easily and cheaply applied to completed typewriters already in use or alternatively incorporated in the machines in the course of their manufacture.

Further objects and advantages of the invention will become apparent as the following description proceeds, taken in connection with the accompanying drawing in which:

Figure 1 is a partial transverse sectional view of a typewriter, embodying the invention, with the electric circuits shown schematically.

Fig. 2 is a rear elevation of the carriage stop mechanism. v

Fig. 3 is a fragmentary detail plan view of the limit switch and a portion of its actuating mechanism included in the machine of Fig. 1.

Fig. 4 is a fragmentary vertical sectional view along the line 4-4 of Fig. 1.

While typewriter attachments embodying the present invention are susceptible of various modiflcations and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment. It is to be understood that I do not intend thereby to limit the invention by such disclosure, but aim to cover 55 all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

In its instant embodiment, the invention has been shown as applied to a so-called motor driven or power actuated typewriter (Fi 1). To avoid 5 driving motor I0 which must be energized to render the machine operative. Upon depressing one or more of the key-levers II a suitable mechanism, driven by the motor i0, is released in a well known manner to cause the usual cone-3 sponding type bar (not shown) to place its imprint on a sheet of paper inserted about the roller or platen 12 on a carriage M.

In accordance with the present invention, a novel attachment has been provided for auto- 26 matically locking the key-levers ll against movement whenever the carriage it reaches its limit or margin-stop position. Furthermore,'the arrangement is such that the key-levers are automatically locked in the event of power failure of the motor l0 and are automatically released whenever the carriage I4 is freed from its mechanical stop, by the usual margin release key, for movement beyond its limit or margin-stop position;

Before proceeding with a description of the attachment noted, the parts of the typewriter cooperating directly with it will first be identifled. The carriage I4 is of conventional form (Fig. 1) being mounted for endwise movement 40 at the rear of the machine frame IE on roller guides I8. 0n the rear of the carriage I4 is fixed a longitudinally extending and notched stop bar H (see also Fig. 2) which forms part of a conventional mechanical stop mechanism for 5 stopping the carriage when it reaches a predetermined limit or margin-stop position. Adjustable along this stop bar I! is a margin stop l8, engaged with selected teeth on the stop bar to determine the limit of travel for the carriage ll. 50 Cooperating with the stop I8 is a stop member or lever is presenting at its left hand end a lug I! (Fig. 1) located in the path of a complemental projection II on the'stop l8 and engageable with it. Upon engagement of the pro- 3 jections i8 and Hifurther travel of the carriage I5 is positively arrested.

The stop member l9 comprises an elongated sheet metal lever having an elongated slot 20 fashioned in its central portion. A pin 2| extends through this slot 20 and pivotaily supports the lever IQ for limited swinging movement in a vertical plane. The pivotal supporting pin 20 extends between and is fixed to the jaws of a bifurcated sheet metal supporting member 22 which is fixed on the stationary machine frame IS. The stop lever I9 is yieldably urged to the left (as viewed in Fig. 2) by contractile spring 23 anchored at its opposite ends to the supporting member 22 and to a depending lug 24 on the right hand end of the lever I9. In this way the stop lever I9 is supported for yielding bodily movement in an endwise direction and is normally biased by the spring 23 to the left hand extremity of its path of endwise niovement' It will be appreciated that when the stop l8. strikes the lug l9 on the lever IS, the latter will be shifted endwise a short distance determined by the length of the slot 20. This endwise movement of the stop member [9, incident to engage- 'ment of it by the margin stop it, is utilized in controlling the key-lever locking mechanism, as will hereinafter appear.

The key levers i I are of conventional form and are located in the usual manner at the forward or key board portion of the typewriter. The forward ends of these key-levers are received in guide slots 25 (Fig. 1) fashioned in a sheet metal channel 26. It will be noted that the downward motion of the key-levers i I when they are struck by the operator, is quite small as is usually the case in motor driven typewriters. Since only a small amount of key lever motion is required in the machine, it will be appreciated that the difficulties of providing an efiectual locking mechanism are enhanced.

The main driving motor it has been shown simply diagrammatically. It may be energized from any suitable source of electric current to which the supply lines L1-La are connected. such, for example, as an ordinary electric light circuit. Connections from the motor to the supply lines are completed through conductors 27, 28 in one of which is interposed a manually operable on-off switch shown in the form of a tumbler switch 29 mounted at some convenient point on the machine. When the switch is closed the supply line L1 is connected by it to the motor conductor 27 while the other supply line In is permanently connected to the conduc tor 28.

Turning now to the key locking attachment herein shown, it will be seen, upon reference to Fig. 1 that it includes a locking blade or bar 3!). This blade is generally rectangular in form, being preferably fashioned as a sheet metal stamping, and is pivoted at its lower edge on a horizontal pin 3i to swing in a counterclockwise direction from its key-lever engaging position shown to a released position in which it is tilted downward sufiiciently to clear the lower edges of the key-- levers. This locking blade is normally biased into locking position by a contractile spring 32 anchored at its opposite ends respectively to the locking blade and to the machine frame it. When the locking blade 3 is in its locked position it presses the key-levers ii firmly upward against the upper ends of the guide slots 25 in the channel 26 and thus efiectually prevents depression of the keys by the operator.

Release of the locking blade 30 is accomplished by the energization of a solenoid 33 (Fig. 1). Axially movable within this solenoid is a cooperating armature 35, which is connected through a yieldable spring 35 with an integral arm 36 5 projecting from the locking blade 30 at substantially right angles with respect to the latter. The

spring 35 is interposed in the system so that upon energization of the solenoid the armature 34 will be drawn almost instantly within the confines of 10 the solenoid and increase its inductive reactance,

to prevent the solenoid from being burned out. even though the force thus stored up in the spring 35 by stretching the latter requires a slightly longer interval of time to pull the' lock- 15 ing blade free of the frictionally engaged keylevers H,

Such an electromagnetically released locking mechanism has a number of advantages as compared to a purely mechanical locking system. First, it is easier to apply to an existing machine. Second, the necessary controls for actuating the locking mechanism are very materially simplified. Third, strong and positive actuation of the locking mechanism is insured and danger of inadvertent movement to locked position, due to vibration of the machine incident to its use, is obviated. Fourth, the locking mechanism can be easily interlocked by electrical circuits with the main driving motor so as to insure automatic so locking of the key board in the event of power failure for the motor.

By connecting the solenoid 33 in parallel with the motor it (Fig. 1) the interlocking of the motor and key-lever locking mechanism for the 35 purpose noted above is accomplished. In the particular arrangement shown, one terminal of the solenoid 83 is connected to a corresponding terminal of the motor l0 through a conductor 3'! while the other terminals are connected through 40 a conductor 88. A suitable dropping resistor 39 is inserted in the conductor 37 in the event that the solenoid 33 is wound for a lower voltage than the rated voltage of the motor. With the connection shown it will be seen that the solenoid 33 5 is connected inside the switch 29 so that this switch serves to energize and deenergize simultaneously both the solenoid and motor.

In order to release the locking blade 30 for movement to its locking position when the car- 50 riage It reaches its limit position, a control switch, designated generally by the numeral 50 (Figs. 1 and 3) is arranged to open-circuit the solenoid 83 in response to the endwisedisplacement of the stop member l9 incident to its being 55 struck by the stop it. The switch 50 is a socalled micro-switch and includes a movable contact 6i normally urged to closed position with respect to a fixed contact 62 and moved to open position by the displacement of an actuating pin 60 63. This switch is interposed in series with the solenoid 33 in the latters supply conductor 38 so that upon opening of the switch the solenoid is deenergized. A generally L-shaped bracket 6%, fixed on the right hand end of the stop member it (Fig. 2) is positioned to engage the switch actuating pin 63 to open the switch when the yond its limit position as, for example, to finish a word which the operator is typing, the usual margin release key 46 (Fig. l) is provided. This key has a long stem 43 mounted for endwise movement and engageable at its inner end with a bell crank 41 pivoted on the frame at 48. The opposite end of the bell crank ispivotally connected at 49 with a lever 50 having a hook shaped upper end and inserted in a generally rectangular'opening 5| (Fig. 2) in the right hand end of the stop member IS. A link 53 and a contractile spring 52 (Fig. 1) anchored to the lever 50 and to the frame l5, serve to hold the lever 50 in generally upright position during its vertical movement incident to oscillation of the bell crank 41. The opening 5| is of sufficient length that the nose of the bell crank will not interfere with the endwise movement of the lever I9. When the margin release key 45 is depressed the bell crank 41 is oscillated in a clockwise direction (as viewed in Fig. 1) thus moving the lever 50 upwardly and thereby swinging the stop member IS in a counterclockwise direction (as viewed in Fig. 2). Such movement of the stop member disengages its lug I9 from the complemental lug I 8 on the stop I8 so that the carriage movement can be continued as desired. At the same time the bracket 44 on the opposite end of the stop member I! is disengaged from the switch actinating pin 43 so that the switch 40 is permitted to reclose, thereby reenergizing the solenoid 33 and unlocking the key-levers II.

The operation of the typewriter shown will in general be clear from the foregoing. In brief, to condition the machine for use the operator closes the on-off switch 29, thereby connecting the motor l and solenoid 33 to the supply lines 1r11n. The resultant energization of the solenoid 33 causes it to draw down its armature 34,

All thereby swinging the locking blade 30 counterclockwise (Fig. 1) into unlocked position. Having thus freed the key-levers II for use the operator proceeds to type a line in the usual manner.

At the end of the line of typing the stop l8 engages the stop lever l9 and thus positively and mechanically stops the carriage l4 in its predetermined limit or margin-stop position. At the same time the resultant endwise shift of the lever l9 opens the switch 40. This deenergizes the solenoid 33 so that the spring 32 pulls the blade 30 back into locking position. By virtue of this automatic locking of the key-levers II the possibility is precluded of depressing a number ofkeys after the carriage is stopped and thus ruining the sheet by superimposing a number of characters at the end of the line.

Upon returning the carriage I4 to its starting position the lever I9 is freed by the stop l8 and is returned to its left hand position (Fi 2) by the spring 23. Accordingly, the switch 40 is permitted to reclose and the solenoid 33 reenergized to unlock the key-levers ll automatically for the next line of typing. Similarly, if the operator wishes to finish out a word at the end of the line the margin release key 45 (Fig. 1) is depressed. This swings the lever l9 6011111381! clockwise (Fig. 2) freeing it from the stop l8 and also from the switch actuating pin 43. In this way thereleasing solenoid 33 is reenergized an the key-levers H unlocked.

In the event of a power failure on supply lines L1L2 the motor In is, of course, stopped, and in the present machine the solenoid 33 is deenergized as well. Consequently, the key-levers ll ment to an existing machine is a simple matter.

The switch 40 can be mounted on the rear of the frame [5 in an easily accessible position and a suitable bracket 44 fixed to the existing lever l9 to actuate the switch. Similarly, the solenoid 33 and locking mechanism can be mounted in the available space beneath the key-levers and the solenoid easily wired into the motor circuit. If the attachment is to be built into a machine during its manufacture it is manifest that its inclusion is a simple matter and requires but a few inexpensive parts.

I claim as my invention:

1. In a typewriter, the combination of a power-driven actuating mechanism including an electric motor, a plurality of key-levers for controlling said mechanism, a releasable locking mechanism movable into and out of locking position for locking said key-levers against movement when in locked position, means normally urging said locking mechanism into locking position, means including an energizable electromagnet for releasing said locking mechanism in response to energization of the electromagnet, a carriage, mechanical stop means for arresting said carriage in a predetermined limit position,

means including a switch for deenergizing said electromagnet to permit said locking mechanism to lock said key-levers, means for actuating said switch in response to engagement of said stop means, and means for energizing said motor and said electromagnet in parallel from a common electric circuit, whereby a power failure resulting in deenergization of said motor will also deenergize said electromagnet to permit said locking mechanism to lock said key-levers.

2. In a typewriter, the combination of a plurality of key-levers, a carriage having a margin stop thereon, movable means for releasably locking said key-levers, means for releasably maintaining said locking means in locking position, means including an electromagnet having an energizing circuit for releasing said locking means, a stop member located in the path of said margin stop and disposed for yielding bodily movement, and a switch interposed in said electromagnet circuit and having an actuating member projecting into position to be engaged and moved into switch-opening position by said stop member upon displacement of the latter by said margin stop.

3. In a typewriter, the combination of a plurality of key-levers, a locking member movable into and out of lockingengagement with said key-levers, means normally biasing said locking member into locking engagement with said keylevers, means including an electromagnet for moving said locking member to released position, said electromagnet having an energizing circuit with a switch interposed in it, a carriage, and means for not only stopping said carriage in a predetermined position but for also substantially simultaneously opening said switch to deenergize said electromagnet, and thereby permit said looking member to return to its normal key locking position.

4. In a typewriter, the combination of a traversable carriage, means including a pair of enrality of key-levers, a carriage having a margin cated in the path of said margin stop and disstop thereon, means for releasably locking said key-levers, means yieldably urging said locking means into locking position, means including an electromagnet having an energizing circuit for releasing said locking means, a stop member 10- posed for yielding bodily movement, a switch interposed in said electromagnet circuit-and having an actuating member projecting into position to be engaged and moved into switch-opening position by said stop member upon displacement of the latter by said margin stop, and means including a margin release key for substantially simultaneously shifting said stop member out of engagement with both said margin stop and said switch actuating member.

6. In a typewriter, the combination of a stationary frame structure, a plurality of key-levers located on the front portion of said structure, a carriage traversable endwise along the rear portion of said structure, an elongated horizontally disposed stop lever located at the rear of said structure and extending along the path of said carriage, pivot means at'the central por-- tion of said lever supporting it for pivotal movement in a vertical plane and for yielding bodily endwise movement, a margin stop adjustably mounted on said carriage and engageable with one end portion of said lever to arrest carriage movement, means movable into and out of looking position for locking said key-levers, means yieldably urging said locking means into locking position,- means including a switch for ef-- end portions from said margin stop and said switch actuating member.

MARTHA F. COOKE. 

